Blame the moon for those jellyfish swarms

There's a reason those bands of marauding jellyfish show up suddenly in the summer months to unsettle beachgoers the world over, and it's been right in front of our eyes this whole time: the moon!

Scientists have long been perplexed by the phenomenon of jellyfish swarms, but Israeli researcher Avi Algazi thinks he has found the answer. His important discovery could help with jellyfish outbreaks the world over.

Studying the swarms of jellyfish that appear in the Mediterranean waters along Israel's coast each summer, Algazi determined that 94% start to arrive approximately 176 days after the start of the year. They are at their height of invasion when the waters reach temperatures between 82 and 86 degrees Fahrenheit and the lunar calendar is in a full moon phase.

According to Algazi, jellyfish did appear when the moon was in other stages, or when the sea temperature was a different temperature than those cited. But such occurrences were infrequent, and were usually characterized by a small number of jellyfish.

Beaches around the world – like this one in Tel Aviv, Israel – attract both people and jellyfish during the summer. (Photo: Sakala/Shutterstock)

The 50-year-old Algazi, who returned to school to get a masters degree, works for the Israel's electric company. They have five power stations located along the coast of the Mediterranean Sea that are inundated with jellyfish during the same period each year. He conducted the research in order to understand why this was so.

"It is possible that individual jellyfish will also reach the coast during other conditions, but we discovered that the most significant swarms arrive under the above conditions," Algazi said. "The proof being that in such periods the number of blockages of the electricity company's cooling facilities due to jellyfish have been incomparably greater than during other periods of the year."

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Zach Pontz
is a writer and photographer for From The Grapevine. In his spare time he likes to wander random cities.